[dm-devel] [PATCH] [PATCH] option to multipath to not modify the bindinfs file

[Malahal Naineni]

Christophe, Hannes: any comments on this approach to fix the uuid issue
reported earlier here
http://permalink.gmane.org/gmane.linux.kernel.device-mapper.devel/12027

Thanks, Malahal.

Malahal Naineni [malahal at us.ibm.com] wrote:
> initramfs is mounted read-write causing multipath to update the
> initramfs bindings file and name all multipath devices it finds using
> friendly names. The actual changes to the file are thrown away as they
> are only written to the memory image rather than to the disk image. This
> may cause the in memory updated initramfs bindings file inconsistent
> with the actual bindings file in the active root file system image when
> devices are added or removed.
> 
> In other words, the boot time updated initramfs bindings file may have
> 'uuid1 map to mpatha' and 'uuid2 map to mpathb', but the active root fs
> bindings file may have 'uuid1 map to mpathb' and 'uuid2 map to mpatha'
> 
> The option, -B, will not modify the bindings file. It will only use the
> bindings file if needed.  This option to multipath should be used when
> invoked in the initramfs context to avoid the inconsistency.
> 
> Signed-off-by: Malahal Naineni (malahal at us.ibm.com)
> 
> diff -r b359f4953289 -r e2c6d0d327f6 libmultipath/alias.c
> --- a/libmultipath/alias.c	Sun Aug 15 10:48:09 2010 -0700
> +++ b/libmultipath/alias.c	Mon Aug 16 13:02:41 2010 -0700
> @@ -353,7 +353,8 @@ allocate_binding(int fd, char *wwid, int
>  }
> 
>  char *
> -get_user_friendly_alias(char *wwid, char *file, char *prefix)
> +get_user_friendly_alias(char *wwid, char *file, char *prefix,
> +			int bindings_read_only)
>  {
>  	char *alias;
>  	int fd, scan_fd, id;
> @@ -394,7 +395,7 @@ get_user_friendly_alias(char *wwid, char
>  		return NULL;
>  	}
> 
> -	if (!alias && can_write)
> +	if (!alias && can_write && !bindings_read_only)
>  		alias = allocate_binding(fd, wwid, id, prefix);
> 
>  	fclose(f);
> diff -r b359f4953289 -r e2c6d0d327f6 libmultipath/alias.h
> --- a/libmultipath/alias.h	Sun Aug 15 10:48:09 2010 -0700
> +++ b/libmultipath/alias.h	Mon Aug 16 13:02:41 2010 -0700
> @@ -8,5 +8,6 @@
>  "# alias wwid\n" \
>  "#\n"
> 
> -char *get_user_friendly_alias(char *wwid, char *file, char *prefix);
> +char *get_user_friendly_alias(char *wwid, char *file, char *prefix,
> +			      int bindings_readonly);
>  char *get_user_friendly_wwid(char *alias, char *file);
> diff -r b359f4953289 -r e2c6d0d327f6 libmultipath/config.c
> --- a/libmultipath/config.c	Sun Aug 15 10:48:09 2010 -0700
> +++ b/libmultipath/config.c	Mon Aug 16 13:02:41 2010 -0700
> @@ -458,6 +458,7 @@ load_config (char * file)
>  	conf->minio = 1000;
>  	conf->max_fds = 0;
>  	conf->bindings_file = DEFAULT_BINDINGS_FILE;
> +	conf->bindings_read_only = 0;
>  	conf->multipath_dir = set_default(DEFAULT_MULTIPATHDIR);
>  	conf->flush_on_last_del = 0;
>  	conf->attribute_flags = 0;
> diff -r b359f4953289 -r e2c6d0d327f6 libmultipath/config.h
> --- a/libmultipath/config.h	Sun Aug 15 10:48:09 2010 -0700
> +++ b/libmultipath/config.h	Mon Aug 16 13:02:41 2010 -0700
> @@ -74,6 +74,7 @@ struct config {
>  	int rr_weight;
>  	int no_path_retry;
>  	int user_friendly_names;
> +	int bindings_read_only;
>  	int pg_timeout;
>  	int max_fds;
>  	int force_reload;
> diff -r b359f4953289 -r e2c6d0d327f6 libmultipath/propsel.c
> --- a/libmultipath/propsel.c	Sun Aug 15 10:48:09 2010 -0700
> +++ b/libmultipath/propsel.c	Mon Aug 16 13:02:41 2010 -0700
> @@ -245,7 +245,7 @@ select_alias (struct multipath * mp)
>  		if (conf->user_friendly_names) {
>  			select_alias_prefix(mp);
>  			mp->alias = get_user_friendly_alias(mp->wwid,
> -					conf->bindings_file, mp->alias_prefix);
> +					conf->bindings_file, mp->alias_prefix, conf->bindings_read_only);
>  		}
>  		if (mp->alias == NULL)
>  			mp->alias = dm_get_name(mp->wwid);
> diff -r b359f4953289 -r e2c6d0d327f6 multipath/main.c
> --- a/multipath/main.c	Sun Aug 15 10:48:09 2010 -0700
> +++ b/multipath/main.c	Mon Aug 16 13:02:41 2010 -0700
> @@ -350,7 +350,7 @@ main (int argc, char *argv[])
>  		condlog(0, "multipath tools need sysfs mounted");
>  		exit(1);
>  	}
> -	while ((arg = getopt(argc, argv, ":dhl::FfM:v:p:b:r")) != EOF ) {
> +	while ((arg = getopt(argc, argv, ":dhl::FfM:v:p:b:Br")) != EOF ) {
>  		switch(arg) {
>  		case 1: printf("optarg : %s\n",optarg);
>  			break;
> @@ -364,6 +364,9 @@ main (int argc, char *argv[])
>  		case 'b':
>  			conf->bindings_file = optarg;
>  			break;
> +		case 'B':
> +			conf->bindings_read_only = 1;
> +			break;
>  		case 'd':
>  			conf->dry_run = 1;
>  			break;
> diff -r b359f4953289 -r e2c6d0d327f6 multipath/multipath.8
> --- a/multipath/multipath.8	Sun Aug 15 10:48:09 2010 -0700
> +++ b/multipath/multipath.8	Mon Aug 16 13:02:41 2010 -0700
> @@ -6,7 +6,7 @@ multipath \- Device mapper target autoco
>  .RB [\| \-v\ \c
>  .IR verbosity \|]
>  .RB [\| \-d \|]
> -.RB [\| \-h | \-l | \-ll | \-f | \-F \|]
> +.RB [\| \-h | \-l | \-ll | \-f | \-F | \-B \|]
>  .RB [\| \-p\ \c
>  .BR failover | multibus | group_by_serial | group_by_prio | group_by_node_name \|]
>  .RB [\| device \|]
> @@ -47,6 +47,9 @@ flush a multipath device map specified a
>  .B \-F
>  flush all unused multipath device maps
>  .TP
> +.B \-B
> +treat the bindings file as read only
> +.TP
>  .BI \-p " policy"
>  force maps to specified policy:
>  .RS 1.2i
> 
> --
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